Should all patients undergoing cardiac catheterization or percutaneous transluminal coronary angioplasty receive oxygen?

Background: Supplemental oxygen is routinely administered to patients with acute coronary syndromes. The risk of significant morbidity during cardiac catheterization or coronary angioplasty has been well described; however, to our knowledge, the need for routine oxygen supplementation in these patients has not been investigated. Methods: In phase 1, we prospectively studied 142 patients undergoing diagnostic cardiac catherization (n = 94) or percutaneous transluminal coronary angioplasty (PTCA) (n = 48) to determine the incidence of procedure-related hypoxemia (pulse oximetry derived oxygen saturation [SpO₂] < 90 percent of > 1 min duration) while breathing room air (RA). In phase 2, 134 patients undergoing diagnostic cardiac catheterization (n = 78) or PTCA (n = 56) were randomly allocated to breathe either RA or supplemental oxygen (O₂, 6 L/min by nasal cannula) to determine the effect of oxygen administration on procedure-related hypoxemia. Oximetry results were compared with pertinent clinical and procedural data that might predispose patients to develop hypoxemia. Results: Phase 1-Moderate to severe hypoxemia occurred in 36 percent (34/94) of patients undergoing diagnostic catheterization and in 56 percent (27/48) of patients undergoing PTCA. In the diagnostic catheterization group, there were a total of 25 episodes of moderate hypoxemia (SpO₂ 85 to 89 percent) lasting 4.0 ± 4.3 min and 11 episodes of severe hypoxemia (SpO₂ < 85 percent) of greater duration, 11.7 ± 7.5 min (p < 0.008). In the PTCA group, there were 24 episodes of moderate hypoxemia and six episodes of severe hypoxemia lasting 4.8 ± 4.3 min and 8.2 ± 3.8 min, respectively. A history of chronic lung disease was associated with hypoxemia (p < 0.05) in the diagnostic group. In addition, 11 patients undergoing diagnostic catheterization who had baseline SpO₂ < 95 percent all developed hypoxemia during the procedure. In this subset of patients, there was a higher incidence of cigarette smoking (p = 0.02), chronic lung disease (p = 0.04), higher left ventricular diastolic pressure (p = 0.02), and lower ejection fraction (p = 0.002) when compared with the 83 remaining patients undergoing diagnostic catheterization with a baseline SpO₂ > 95 percent. Phase 2-Oxygen therapy was associated with a reduction in the incidence of hypoxemia from 42 percent to 5 percent (RA vs O₂, p < 0.001) in the diagnostic catheterization group and 39 percent to 11 percent (RA vs O₂, p < 0.03) in the PTCA group. Conclusions: Significant hypoxemia is a common finding among patients undergoing cardiac catheterization or angioplasty despite the absence of predictive risk factors. Severe and prolonged hypoxemic episodes occurred in 10 percent (14/142, phase 1) of patients breathing room air. Patients undergoing diagnostic catheterization with history of chronic lung disease or a baseline SpO₂ < 95 percent are at high risk to develop moderate-severe hypoxemia. Oxygen therapy significantly reduced the incidence and severity of procedure-induced hypoxemia in both groups. Our data support the use of both pulse oximetry and oxygen supplementation in patients undergoing cardiac catheterization and PTCA.